We shall continue to treat opiate-dependent persons with naltrexone, a narcotic antagonist. The patients are recruited from a therapeutic community program rather than the usual sources. Treatment is aimed at preventing relapse during critical periods following release from the hospital or the constraints of the program. The work is handicapped by a high dropout rate, characteristic of all such populations of opiate-dependent persons. Such treatment might be greatly facilitated by the availability of a depot preparation. Naltrexone will also be used in normal persons to determine whether antagonism of endogenous opioids has any appreciable effect on the mood, cognitive or motor functions of such subjects.